The present invention relates to impact hammers for driving elongate members such as piles into the earth and, more specifically, to hydraulic impact hammers having low headroom for use in restricted access locations.
Construction projects often require elongate members to be driven into the earth. In the present application, the term xe2x80x9celongate memberxe2x80x9d shall refer to any member that must be forced, driven, crowded, or pounded into the earth. Examples of elongate members include metal or wooden piles, caissons, wick drain mandrels, and the like.
A number of techniques are commonly used to drive elongate members into the earth. For example, elongate members may be driven into the earth by an impact hammer (hydraulic and/or gravity driven) that pounds on the exposed end of the elongate member, a vibratory device that imparts a relatively high frequency up and down motion on the elongate member, a gear or wheel drive system that engages the sides of the elongate member, a cable and pulley system that exerts a crowding force on the top of the elongate member, or some combination of these techniques. The present invention is an impact hammer device.
The present invention is of particular use in environments, such as under a bridge, having restricted headroom. An impact hammer device employs a ram member that is raised and then dropped against the upper end of the elongate member being driven. The act of raising and dropping requires at least enough headroom to accommodate the vertical height between the raised height and the dropped height. Additional headroom is required by the structure employed to raise and lower the ram member. One purpose of the present invention is to reduce the headroom required by an impact hammer device.
The Applicant is aware of prior art single-acting pile hammers sold by MKT Corporation under model numbers MS350 and MS500. These pile hammers include a ram assembly comprising a ram member defining a cavity and cylinder cover that covers the cavity. The ram assembly forms a cylinder for a pneumatic piston assembly. A piston rod extends through the cylinder cover such that a piston head is located within the cavity. Air under pressure is introduced into the cylinder above the piston head to raise the ram member. When fully raised, the pressurized air is released from the cylinder to allow the ram member to drop and impact a pile or other elongate member to be driven. The released air is simply vented to the atmosphere.
The arrangement of the MKT systems effectively locates the lifting apparatus within the ram member and connects the lifting apparatus to the bottom of the ram member. The overall height of the pile hammer is thus reduced, making these systems appropriate for use in low headroom situations.
The MKT systems have relatively limited driving capacity for the total volume of the system. The need thus exists for low headroom impact hammer systems with increased driving capacity for a given volume occupied by the system.
The present invention is an impact hammer system for driving an elongate member. The impact hammer system comprises a ram member, a frame assembly, an actuator assembly, and a power source. The ram member defines a ram bore. The frame assembly supports the ram member such that the ram member may move relative to the frame assembly between first and second positions. The actuator assembly is operatively connected between the frame assembly and the ram member and is operable in extended and retracted configurations.
At least a portion of the actuator assembly is disposed within the ram bore and a substantial portion of the actuator assembly extends out of the ram bore when the cylinder is in the extended position. The power source is operatively connected to the actuator assembly to place the actuator assembly in the extended and retracted configurations. Extension and retraction of the actuator assembly moves the ram member between the first and second positions, respectively. The ram member impacts the elongate member when the ram member moves into the second position.